Radiation



FehZ 1938. H. KQTT 2,109,235

RADIATION FILTER AND METHOD FOR UTILIZING THE SAME Filed June 29. 1935 2 Sheets-Sheet 1 TU 4 f/W eenefaeo/ Ce//a/ose l N V E NTOR .Haw/WANN KD7-r.

BY Mmm ATTO RN EYS Feb. 22, 1938.

H. KOTT RADIATION FILTER AND METHOD FOR UTIL'IZING TIIE SAME Filed June 29. 1935 2 Sheets-Sheet 2 INVENTOR *ATTORNEYS Patented Felpa-2, 1938 PATENT' oFFicE nimm'rlon m'rEn. AND ME'rnon Fon. U'nuzlNG 'run SAME Hermann Kott, East Orange, N. J., assigner, by mesme assignments, -to Ion Corporation, Short Hills, N. J., a corporation of New Jersey.

Application June 29, 1935, Serial No. 29,095

1' claim. (ci. 25o-s4) This invention relates to radiation measuring and detecting devices and more particularly to radiation lter means for use in connection with the measuring and detecting o f radiation.

`One of the objects of the present invention is to provide a radiation lter for use in the detection of radiation within certain wavelength ranges. Another object is to provide means for detecting and measuring radiation within certain wavelength ranges. y to provide an improved method and means for the detection and measurement of radiation. Other objects and advantages will be apparent as the invention is more fully disclosed.

In accordance` with these objects, I have discovered that Acellulosic material, particularly radiation permeable cellulosic material such as rey generated cellulose, can be utilized as a radiation iilter by incorporating within the cellulose a pro- 0 portion of a'salt such as cobalt chloride which has the property of changing its color or color intensity with respect to its moisture content. Thereafter by incorporating within the cobalt impregnated cellulose suicient water to impart thereto a desired color intensity the material may be employed as a radiation lter.

Upon the projection of radiation through 'the cobalt and moisture impregnated cellulosic material upon a radiation sensitive device the said device responds to and measures the amount of such radiation which is not absorbed by the iilter.

This phenomenon may be utilized in a number of different ways, and in the accompanying drawings I have illustrated several adaptations. In the drawings Fig. 1 illustrates schematically one specific embodiment of the present invention; Fig. 2vis a view along plane 2-2 of Fig. 1; Fig. 3 illustrates schematically a second specic embodiment of the present invention; Fig. 4 illustrates schematically a modiiication of the specic embodiment of Fig. 3;` Fig. 5 illustrates schematically a second modiiication of the specific embodiment of Fig. 3; Fig. 6 is an enlarged schematicl View of a further modication of the em- Still another object is y by means of reiiector 2 through filter element 3 upon radiation sensitive device 4 which regulates the iiow of energy in external electric circuit 5 including meter 6 and source of direct electric current 1. Radiation sensitive device 4 may be any of the well known types of photo or radiation sensitive cells or tubes heretofore proposed in the art.

Filter element 3 is comprised in accordance with the present invention preferably of regenerated cellulose impregnated with cobalt chloride. Regenerated cellulose contains a proportion of glycerine approximating 14 to 16 per cent and is characterized by the property of absorbing moisture from an atmosphere and of giving up moisture to the atmosphere relatively rapidly in response to variations in themoisture content of the atmosphere. The ultimate or equilibrium moisture content of the cellulose bears a substantially constant ratio to the humidity of the atmosphere with any given cellulosic material which can be calibrated. The eiect of temperature upon this constant ratio also may be calibrated.

Accordingly, in the determination of atmospheric humidity lter element 3 may be comprised for example of a relatively thin sheet of cobalt chloride impregnated regenerated cellulose which is suspended in the atmosphere in such manner that the atmosphere will -freely contact with both faces. The beam of radiation A from source I may be focused to irradiate a relatively large surface area of the filter element and means (not shown) may be employedl to focus the filtered beam upon the radiation sensitive surface of photo-electric tube or cell 4.

The amount of-cobalt chloride to be impregnated in the radiation permeable cellulosic material may vary widely without departing essentially from the nature and scope of the present invention, depending upon the contemplateduse thereof. In the adaptation of the filter to the use indicated in the specific embodiment of Fig. 1 the intensity of'radiation and kind o'fradiation emitted by source i may control the amount of cobalt chloride required. So also the humidity range of the atmosphere may govern the amount of cobalt chloride required.

An ordinary incandescent lament lamp demits radiation of a wide range of wavelengths.` The. color range in lter element 3 may be made to vary with variation in cobalt chloride content and moisture content in the lter from very light rose to very dark purple thereby cutting oir or filtering out radiation having wavelengths within this color band. For the purpose of measuring the,l variations in the humidity of the atmosphere. the degree of accuracy sought may also control the color range employed. For example, it may be desirable to obtain but three measurements such as low, medium and high humidity. In such case, the amount of cobalt chloride employed may be adjusted such` that Vwith high humidity the filter remains substantially unchanged in color; with medium humidity the filter assumes color; and with low humidity the illter takes on a very dark color.

For accurate measurement of the humidity. it is preferable to employ as a light source I a special lamp which emits radiation relatively high in radiation oi' wavelengths within the color band of the filter 3. such as a. mercury arc, glow discharge, or ultra-violet lamp. Such devices are readily available on the market today. With this kind of radiation passing through filter 3 the variations incident to absorption by the lter through changes in color due to moisture absorption from the atmosphere may be readily detected and measured.

In the modiiication illustrated in Fig. 3 filter element 3 is enclosed within a housing 3 provided with radiation permeable windows 3 and I0 within which housing means II is provided whereby an atmosphere at a substantially constant humidity may be maintained. In this arrangement, lter 3 thereby is given a determined color and is permeable to radiation oi' wavelengths below this color range. By projecting radiation emitted from source I through an auxiliary filter 3' before passing the radiation through filter 3 a narrowedI band oi' radiation wavelengths thereby may be detected and measured by the external circuit 5 including means 6 and 1. Auxiliary filter 3', for example. may exclude red and infra-red radiation and filter 3 may be colored by the humidity of the atmosphere enclosed within housing 8 to exclude all radiation above about 3100 Angstrom. Light source I, for example, may be an incandescent filament lamp as shown or may be a tungstenmercury arc lamp emitting relatively large quantities of radiation in the violet and ultra-violet range of wave-lengths. By the arrangement indicated in Fig. 3 relatively accurate measurement of the amount of radiation below a certain wavelength (limited by the color imparted to fllter 3) emitted during any given unit or period of time by light source I may be determined.

In the modification illustrated in Fig. 4, the detection and measurement of the radiation is obtained by the use of a radiation sensitive device I I and circuit means |2.

Device is substantially a gaseous conduction device and comprises an enclosing radiation permeable envelop II, a pair of spaced electrodes I3 and I4 and a pressure of ionizable gas. The electric circuit I2 includes means I5 to impress a potential upon electrodes I3 an'd I4 which is substantially less than the breakdown potential therebetween; and means I6 to balance the external circuit resistance with the internal resistance of the device I| to permit the ow of a leakage current between the electrodes across the intervening gas path. 'I'his current flow is impressed upon grid I1 of thermionic amplifier device I3 containing an indirectly heated cathode rI3 and a. pair of anodes 20 and 2| which are electrically connected in parallely across potentiometer 22 to a source of plate voltage 23. Variable resistances 24 and 25 are provided in each plate circuit to permit the adjustment of the circuit resistances in each plate circuit so that with any given grid voltage on grid I1 the current drawn through tube I3 by both plate circuits is substantially equal and potentiometer 22 thereupon registers gere.

Thereafter//upon changing the internal resistance by tube I by projecting radiation therethrough in the manner indicated, the increase or decrease in current flow through device II varies the potential upon grid I'I which in turn a1- ters the plate current drawn by the closer spaced plate electrode 2|. This is indicated by the deilection in potentiometer 22 substantially as indicated.

In the modification indicated in Fig. 5, the external circuit I2 has been changed to provide for operation directly from an alternating current source instead of a direct current source as indicated in Fig. 4. Rectiiler 23 energized by alternating current from source 21 supplies a pol tential of rectified current to resistance 28 provided with tap connections 29 and 30 from which potentials suitable to replace direct current sources I5 and 23 respectively may be drawn. The remaining elements are substantially the same as those heretofore described in Flg.4.

In adapting the modifications of Figs. 4 and 5 to the detection and measurement of ultra-violet radiation, the structure indicated in Figs. 6, 7 and 8 has been devised. In Fig. 6 the radiation sensitive device II is shown totally enclosed by the filter heretofore identified by numeral 3, and hence is responsive to such radiation as may pass through the said filter.

To obtain this result, I comprise illter 3 of cup or closed end tubular shaped regenerated cellulose material 3|, which is enclosed in a similarly shaped double walled radiation permeable housing 32 having an opening 33 in the base of the outer wall which opens into a chamber 34 enclosing a perforated container 35` which is filled with pieces or chips of regenerated cellulose. Filter 3| is impregnated with cobalt chloride as heretofore described. Chamber 34 and the double walled container 32 are sealed from the atmosphere but communicate with each other through opening 33.

'I'he open end oi' the double wall container 32 is inserted in groove 36 of base element 31 wherein is concentrically located device II. 'I'hus assembled all radiation acting upon device II must pass through lter 3|. The color intensity of the lter 3| is adjusted by introducing within container 32 in any convenient manner an atmosphere having a humidity which with the cobalt chloride content of the filter employed will color the lter 3| to pass radiation below about 2950 Angstrom. This atmosphere is retained therein until the illter 3| and regenerated cellulose particles in container 35 each have reached equilibrium as to water content by absorption from the atmosphere. The device then may be sealed from the atmosphere and within relatively large variations in temperature the color characteristic oi the filter 3| will remain substantially constant'. The particles of cellulose in container 35 act as a stabilirer as with variation in temperature they give up and absorb moisture from the atmosphere at a more rapid rate than does the cobalt impregnated illter 3 I.

'I'his entire assembly of elements may be enclosed in a radiation impermeable housing 38 provided with radiation permeable window 33 preferably of quartz, and the radiation to be and through filter 3| to device ll.

measured projected through the window 3l upon The current flow in device Il is carried through terminals Il an 4I to any of the external circuits heretofore described.

'I'he device oi Figs. 6, 7 and 8 may be widely adapted to a variety oiuses. It is particularly adapted to the detection and measurement of radiationin the violet and ultra-violet range and hence is of special service andutility in therapeutic fields wherein the application of ultra-violet radiation inthe irradiation of food and milk products, the curative treating of persons and the like applications often require that the quantity and kind voi' radiation employed be known and controlled.

Having broadly and specically described the present invention it is apparent that many modiilcations and departures may be made therein without departing essentially from the nature and scope thereof. and all such modifications are contemplated as may fall within the scope or the following claim.

What I claim is:

radiation illter comprising a double walled and domed cylindrical container having an opening in the domed outer wall thereof, a cylindrical and domed sheet of regenerated cellulose impregnated with cobalt chloride enclosed thereby. a hermetically sealed chamber closing said opening from the atmosphere said chamber` enclosing a perforated'container, a quantity of regenerated cellulose within said container and a gaseous atmosphere having a determined humidity enclosed 'within said chamber and container.

. HERMANN KO'I'I. 

